1. Field of the Invention
The present is directed to a method of measuring radio-frequency interference voltages (also called RFI voltages) or RFI energy (RFI currents or RFI field strengths) converted to such RFI voltages within a predetermined frequency range.
2. Description of Prior Art
The measurement of RFI energy such as RFI current, RFI power or RFI field strength is defined in conformity with national and international standards (for instance CISPR, VDE and FCC standards) by measuring regulations and limit values. One of these measuring regulations, for example, is peak-voltage measurement in which the peak voltage levels measured while tuning the frequency range are compared with a predetermined so-called broadband limit level. A further measuring regulation is the so-called quasi-peak measurement in which the interference voltages during measurement are rated by predetermined standardized time constants, for instance to CISPR again. Until recently, these different measurements on the EUT (equipment under test) have been performed successively by corresponding tuning through the entire frequency range. The peak-value measurement can be performed relatively quickly since the measuring time per peak value is only about 30 ms, so that the entire frequency band can be tuned within e.g. three minutes. For the quasi-peak measurement, however, the standard prescribes certain charge and discharge time constants with the result that each such quasi-peak measurement takes at least one second. Hence, the measuring period for such a quasi-peak measurement throughout the entire frequency range is more than one hour.
For noise rating in spectral analyzers it is known per se to measure both the maximum and the minimum peak voltage level during continuous tuning of a predetermined frequency range (spectral analyzer HP 8568 of Hewlett-Packard).